NOx formation in thermal Processes

Alchemist01 · May 22, 2017

Deart All,

can anyone help me to understand how thermal NOx is formed and if possible to show one example how to calculate the formed thermal NOx in thermal applications and please, also if possbile can you tell me the differences in fuel NOx and prompt NOx formation and to show one example how to estimate their formation in one application.

would be glad for your help.
Thanks,
Reagrds,
Analyzer_008

SlideRuleEra · May 23, 2017

Can anyone help me to understand how thermal NOx is formed...

I can briefly cover the basics of thermal NOx production from burning pulverized coal at electric generating stations.

To maximize thermal efficiency, pulverized coal is burned at high temperature. This creates ash (both fly ash & bottom ash) plus sulfur compounds (SOx) from ingredients in the coal.

Bottom ash is granular, like sand, and is easily removed from the bottom of the boiler. Often by sluicing with water.

Fly ash is removed from flue gas with electrostatic precipitators or filters (bag houses).

Next, sulfur compounds are removed from the flue gas with "scrubbers" (flue-gas desulfurization - FGD equipment).

During combustion, necessary high temperatures cause atmospheric nitrogen and oxygen to react creating NOx compounds. Note that neither the nitrogen nor the oxygen comes from coal. On a large scale, the best available technology to remove NOx compounds is "Selective Catalytic Reduction" (SCR). Ammonia is introduced into the flue gas (after both ash and SOx compounds have been removed.) In the presence of a catalyst, ammonia reacts with NOx to create nitrogen (N[sub]2[/sub]) and water vapor.

None of this equipment removes 100% of the pollutants, but electrostatic precipators come close for fly ash removal.

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Alchemist01 · May 24, 2017

Thank you for breif introduction, do you know how the NOx formation dependent on the temperature, I mean higher temperatures means higher NOx, is that right, but can you tell me how it is estimated, assuming I have a flow of waste app. 10000 Nm3/hr (it can be gaseous or liquied waste with no Nitrogen compount in the inlet) and the incineration temperature of app. 1000 °C, in that case can you tell me how much NOx will be formed during incineration, and please, also can you tell me how you estimate it, if you show an exsample calculation I would be very glad.
DO you have any information how SCR is dimensioned, an excell example would be the best , if you have any would be very glad for your help.

thanks in advance a lot.
Regards,